Legend:

Did some more research about old/obsolete HTML3 attributes. They only work if the element has no css styling. On top of that some obsolete attributes are ignored as soon as any css styling is applied, even when there is no direct css style that replaces them.

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In that terms we are not talking about "not loosing data" but rather about preserving obsolete code that introduces inconsistencies.

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In that terms we are not talking about "loosing data" but rather about preserving obsolete code that introduces inconsistencies.

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Since tables were used mostly for layout, the behaviour of obsolete attributed is more consistent there. Perhaps they should be treated as special case. We can set TinyMCE to allow all HTML attributes on them.